JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr>
        <td>
            <input type="checkbox" id="testcheckbox" />
            Is selected?
        </td>
    </tr>
</table>
<hr />
<div id="f1">some content</div>

CSS

#f1{
   visibility: hidden;
}

JavaScript

function changeVisiblity() {
    if ( getContent.style.visibility == "hidden" || getContent.style.visibility == '' ) {
        getContent.style.visibility = "visible";  
    } else {
        getContent.style.visibility = "hidden";    
    }
}

var getCheckbox = document.getElementById("testcheckbox"),
    getContent = document.getElementById("f1");

getCheckbox.addEventListener( 'change', changeVisiblity, null );